CO2 is a new-type eco-friendly refrigerant, which can reduce the greenhouse effect, and solve the environmental pollution of compound, thus has a good economic and practical performance. A compression-type refrigeration cycle system taking CO2 as working medium can be applied to most refrigeration/heating fields.
However, the CO2 refrigeration system has a high working pressure, and this feature of this type of system is required to be fully taken into account when designing a CO2 heat exchanger, and the design of the components is still immature, as a result, this type of system is not widely used. In general, CO2 heat exchangers are mainly of a finned-tube type, a microchannel type, a plate type, a shell-and-tube type, a finned-plate type, a double-pipe type and so on. The plate type and the finned-plate type are complex in manufacturing process, while tubes of the finned-tube type, the tube-in-tube type and the shell-and-tube type require a relatively large wall thickness, which causes a material waste.
Besides, the conventional CO2 microchannel heat exchanger performs heat exchange by the forced convection between the refrigerant and the air, which has a low efficiency. Although there is a large difference between physical properties of the liquid and the air, and the liquid-air heat exchange has a higher efficiency, the liquid-air heat exchanger has problems of a large wall thickness and a low heat exchange performance.
Therefore, a technical problem to be urgently solved is to provide a heat exchanger that is applicable to the refrigerant system having a relatively high pressure and has a good heat exchange performance.